This invention relates to security articles, such as banknotes or other security documents, and is particularly concerned with providing a method and an apparatus for inspecting a security device or devices in one or more security articles.
As used herein, the term “security documents” includes documents and tokens such as identity documents, value documents or entrance documents, which in turn respectively include: passports, visas, identity cards, drivers licences, and security entrance cards, banknotes, shares, bonds, certificates, cheques, lottery tickets, bank cards, charge cards and credit cards, and aeroplane tickets, bus tickets, railroad tickets, and tickets to fun parks or specific rides. These security documents or tokens typically include some form of authenticity verification to guard against copying and fraudulent alteration. It will, however, be appreciated that this invention is applicable to other types of articles which require authentication and/or protection against copying or theft. Such articles, including security documents, are referred to broadly as “security articles” in this specification.
A wide variety of security devices have been proposed for use in security documents for verification of authenticity and to make counterfeiting of the documents difficult. Some types of security devices are low security devices, printed devices or embossings, which are relatively inexpensive to produce in security documents but which only provide a relatively low degree of security. Other types of security devices are high security devices, such as diffraction gratings or holograms. These can provide a higher degree of security because they are more difficult to counterfeit, but are more expensive to produce and so are generally used in higher value security documents, such as $50 or $100 banknotes, when high security devices are provided in banknotes, it is desirable to detect their presence and quality in the production process of the banknotes before the banknotes are issued to the public. It is also desirable to provide apparatus for inspecting a high security device in a single banknote.
WO 99/37488 discloses a security document and method in which a diffractive optical projection element is provided within a transparent portion or window in the document, The diffractive optical projection element transforms a collimated beam of light, e.g. from a point light source or laser, into a patterned beam of a selected design. In the method of verifying the authenticity of the security document described in WO 99/37488, the patterned beam is projected onto a viewing surface, e.g. by folding the security document so that another part of the document laterally spaced from the window acts as the viewing surface. In another embodiment, the security document of WO 99/37488 may include a second transparent portion or window which can act as a pseudo point light source when the security document is folded.
In each embodiment described in WO 99/37488, the authenticity of the security document incorporating the diffractive optical projection element is verified visually by a person viewing the patterned beam when it impinges upon a viewing surface. However, this visual viewing method is not very suitable for inspecting the presence or quality of diffractive optical elements in banknotes or sheets of banknotes in equipment such as printing equipment, note sorting equipment or other equipment used in processing banknotes or the like.